1. Field of the Invention
The present invention relates to a resin composition as a polymer blend which comprises a graft polymer and which has higher compatibility between the component resins and higher performance, as well as to a method for compatibilizing different resins with each other to obtain said resin composition. Said resin composition can be used as a polymer blend capable of responding to diversified requirements for polymer materials, such as higher processability, higher heat resistance, higher impact resistance, higher gas barrier property and the like.
2. Description of the Related Art
Polymer blends each comprising different polymers having different properties have been used for performance improvement of polymer material. Of them, a composition comprising a graft polymer (obtained by chemically bonding two components contained therein), has improved adhesivity and compatibility between the two components and has been used for further performance improvement.
The method for producing a resin composition comprising a graft polymer can be largely divided into two methods. The first method is a method comprising polymerization. It includes a method in which graft reaction sites are introduced during polymer production as seen in the case of maleic anhydride copolymer or macromolecular monomer, and a method in which monomer polymerization is conducted in the presence of a trunk polymer [e.g. Japanese Patent Application Kokai (Laid-Open) No. 58188/1975 and Japanese Patent Application Kokai (Laid-Open) No. 108016/1988].
The second method is a method comprising no polymerization, wherein graft reaction sites are introduced into a polymer having no graft reaction site, in a post-reaction and grafting is conducted between the resulting polymer and a different polymer. It includes a method described in Japanese Patent Application Kokai (Laid-Open) No. 155412/1986 (USP 4937284), etc., which comprises reacting a resin with a peroxide or the like to generate a radical in the resin molecule, reacting the radical with a silane coupling agent to form a graft reaction site, and melt-kneading the resulting resin with other resin to achieve grafting between the two resins.
The second method, as compared with the first method, has advantages that the resins to be subjected to grafting can be selected from many kinds of resins and the whole procedure can be carried out in an extruder. The second method, however, has had a drawback that since the radical introduction into trunk polymer is essential, undesirable irreversible side reactions (e.g. crosslinking, decomposition, etc. of polymer) take place simultaneously with the radical introduction, making impossible the introduction of graft reaction sites in sufficient degree.
Thus, the conventional methods have had problems that a special polymerization method or a copolymer resin of a special component must be used in order to obtain high compatibility and that use of general-purpose resins results in low compatibility.